Fabrication of hollow articles



May 29, 1962 D. K. BLElKAMP ETAL 3,036,370

FABRICATION OF HOLLOW ARTICLES Filed Dec. l0, 1956 United States PatentO 3,03,370 FABRECATIN E HGLLOW ARTICLES Donaid K. Bleiiramp, Berkeley,Mo., and William V. Wenger, Wood River, lll., assignors to OlinMathieson Chemical Corporation, East Alton, lli., a corporation ofVirginia Filed Dec. it), 1956, Ser. No. 627,432 8 Claims. (Cl. 29-157.3)

This invention relates to the fabrication of hollow articles, moreparticularly to an improved apparatus and method for forming the hollowsin such articles.

The invention is more particularly directed to an apparatus and methodfor expanding hollows in panels of the type disclosed in U.S. Patent2,690,002, although the blank from which the hollow panel is formed maybe fabricated by other methods. Certain features of the aforementionedpatent will be described to facilitate a clear understanding of theinvention. The panels described in the aforementioned patent arefabricated by applying a pattern of weld-inhibiting material to a sheetof metal, superimposing a second sheet of metal on the first sheet withthe pattern of weld-inhibiting material sandwiched between the sheets,and welding the two sheets together in their entire adjacent areas notseparated by the weld-inhibiting material by rolling. The resultantpanel is elongated in the direction of rolling and the adjacent faces ofthese sheets are welded together throughout their entire area notseparated by the pattern of weld-inhibiting material. A fluid pressureis then injected into the unjoined portion of the panel to outwardlydistend the sheets in the area of the weld-inhibiting material to form ahollow panel. The panel is posi--v tioned between rigid spaced apartpressure pads and a fluid pressure is then injected into the unjoinedportion o f the blank to outwardly distend the sheets into rrnengagement with the pads thereby providing the hollows with ilat outersurfaces. Hollow panels of this type often require relatively largehollows which serve as tubes or conduits for conveying a fluid. Anexample of such a panel may be found in an evaporator panel forrefrigerators, in which is combined either a circuitous tube design inconjunction with a large boiler or accumulator. The expansion of largehollows of this nature have presented many problems, such as rupturingof the walls of lthe large hollow where it joins the solid web of thepanel, and warping of the web and tube portion of the panel because ofthe strain resulting from the expansion of the large hollow. Thetendency of the large hollow to rupture can be retarded by permittingthe web portion of the panel to pull in, or draw in toward the largehollow thereby permitting a greater outward expansion of the largehollow. However, such drawing in of the panel inevitably results inwarping the web and tube portion of the panel. If the web portion of thepanel is iirmly clamped during expansion of the large hollow, suchwarping is not likely to occur, but under these circumstances, the weband tube portion of the panel cannot.

draw in towards the large hollow and the walls of the large hollow aretherefore more likely to rupture.

In expanding such large hollows the present invention comprehendspositioning the blank between pressure pads spaced iapart just slightlymore than the thickness of the blank, the pads having a cut-out portionadjacent the unjoined inner portion of the blank which is to form thelarge hollow. When the panel has been initially expanded -to providehollows having outer surfaces, the aforementioned difficulties can beovercome by further expanding thedesired 4large hollows as follows. Theinitially expanded panel is positioned between rigid pressure padshaving a cut-out portion to permit additional expansion of the desiredlarge hollow while preventing ICC warping of the web and tube portion ofthe panel. 'I'he web and tube portion of the panel should not be tightlyclamped between the pads because it is desired that the web and tubes bepermitted to draw in toward the large 5 hollow. Large expenses of webdevoid of expanded tubes may be restrained against warping by theprovision of blocks between the pads and the web, or by protrusions onthe pads. Preferably the pads are spaced apart a distance slightlygreater than the outwardly expanded dimensions of the tubes to preventcrushing the tubes as the pads are brought together. Under thesecircumstances, upon injection of a fluid pressure into the previouslyexpanded hollows, the tubes are expanded slightly into engagement withthe pads and the large hollow will be free to expand a much greateramount than the tubes, thereby providing a hollow portion ofsubstantially greater volume than was obtained during the` initialexpansion.

It is therefore an object of this invention to provide an improvedmethod and apparatus for forming relatively large hollows in hollowpanels.

Another object of this invention is to provide an mproved hollow panel.

Additional objects and advantages will become apparent from thefollowing description and drawings from which:

FIGURE 1 is a perspective view of a sheet of metal havin-g a pattern ofweld-inhibiting material applied to a surface thereof.

FIGURE 2 is a schematic perspective view of the sheet as shown in FIGUREl having superimposed thereon a second sheet of metal with the patternof weld-inhibiting material sandwiched between the sheets and showingthe sheets being welded together While passing through a pair of millrolls.

FIGURE 3 is a schematic sectional view of the resultant blank of FIGURE2 positioned between a pair of rigid spaced apart pressure pads andexpanded to form a hollow panel, the portion of the pattern ofweld-inhibiting material forming these hollows being indicated by theline 3 3 in FIGURE l.

FIGURE 4 is a schematic perspective view of an embodiment of restrainingpads and blocks for use in subsequent expansion of the hollow panelshown in FIG- URE 3.

FIGURE 5 is a schematic sectional view of the panel shown in FIGURE 3positioned on the pad and blocks shown in FIGURE 4, with anotherembodiment of a similar pad positioned atop the panel, the section ofthe lower pad and block assembly being indicated by the line 5 5 inFIGURE 4, and the section of the panel being the same as in FIGURE 3.

FIGURE 6 is a schematic sectional view similar to FIGURE 5 after thehollow panel has been further expanded.

Referring to the drawings, FIGURE l illustrates a sheet of metal lhaving applied to a clean surface 2 a pattern of weld-inhibitingmaterial 3. The pattern of weld-inhibiting material includes a strip 4terminating at an edge of the sheet, a plurality of interconnectedstrips 5 and a relatively large area 6 interconnected with the strips 5.FIGURE 2 shows the sheet l having superimposed thereon a second sheet 9with the pattern of weld-inhibiting material 3` sandwiched between thesheets. The sheets 1 and 9 are tacked together as by spot-welds l0 toprevent relative slippage between the sheets as they are subsequentlywelded together by passing through a pair of mill rolls 11 to form ablank 12. It is normally necessary that the sheets l and 9 be heatedprior to passing through the mill rolls to assure that they weld to eachother in keeping with techniques well known in the rolling art. Thesheets il scesero Referring to FIGURE 3, the resultant blank 12 ispositioned between'a pair of spaced apart pressure pads 16. The pressurepads i6 are on relatively movable jaws i A nozzle is inserted into theinlet 4 and l 17 of a press. the unjoined portion of the blank isexpanded into firm engagement with the rigid pressurepads 16 resultingin hollows 18 throughout the blank. These hollows all have flat outersurfaces 19 through engagement with the pads 16. The strips of theweld-inhibiting pattern 3, shown in FIGURE l, form tubes 20 and theVarea 6 forms the large hollow 2,1. The hollows are separated from eachother by solid webs 22. Circumscribing the tubes is a solid flange 23.The iluid pressure within the hollow 18 is now released into pressurepads 16 and press jaws 17 spaced apart a greater distance to permitremoval of the hollow panel 24.

The large hollow 21 is now expanded" a greater amount by positioning thepanel 24 between the restraining means shown-in FIGURE 5. -The .lowerrestraining means 2.7 is shown in perspective in FIGURE 4 and includes arigid restraining pad 28 having a cut-out portion 29. Bositioned onftopsurface 3i) of the pad 28 are a number of blocks 31, 32, 33, and'34.These blocks are slightly thinner than half the total loutwardlyexpanded dimension of the hollows 13, less half the thickness of the web22.0f the expanded panel 24. In other words, the blocks are slightlyless than half` the spacing between-the pads16, shown in FIGURE 3, lesshalf the thickness of the panel web 22. The upper restraining means 35is similar to the lower restraining means 27 except that ,the blocks31-34 lare replaced by integral protrusions such as 36 and 37. Thelarge-hollow 21 is positioned on the lower restraining means 27 adjacentthe cut-out 29. The blocks 31-engage the web 22 and the blocks 32-34engage a portionof the solid flange 23. All edgesof the 'blocks SL34,and the protrusions such as 36 and 37 should be rounded olf adjacent thepanel 24 to prevent mari-ing the surface of the panel. The web 22 shouldbe firmly held inthe press, but should not be tightly clamped betweenthe` restraining means 27 and 35. The tubes 20 or other hollows shouldbe slightly spacedfrom the adjacent portions of the restrain- The blocks31 or the protrusions 36 should be so positioned 4that any large expanseof web which is devoid of tubes 20 or other hollows, is restrainedagainst warping. It is also desirable thatV the panel flange 23 beprevented from warping by use of similar blocks 32-34 or protrusions as37. Portions of the flange which are -to be trimmed from the iinishedpanel need not be restrained Y against warping or buckling as thiswarped portion may be trimmed from the panel.

The restraining means 27 and 35 may be interchanged but if blocks areused in conjunction with the upper restraining means 27 and 35 they willhave to be either individually positioned on the panel 24 after it hasbeen placed Yin the press, or alternately they will have to bepermanently secured to the pad 28. If only a few panels are to befabricated, it will be more economical to position the blocks 31-34 onthe pad 28 and then properly position the panel 24 on the pad andblocks. Subsequently, additional blocks are positioned appropriately onthe upper surface of the panel 24. When the panel has received aninitial expansion, the positioning of the blocks is a relatively simplematter. When a larger number of panels is to be fabrica-ted, it will bemore economical to use a preformed restraining means such as 35, inwhich event the ing means 27 and 35 as will occur if the blocks orprotr'usions-are of the proper thickness as previously described. Suchblocks or protrusions are only necessary to prevent distortion ofrelatively large areas of web, that is, areas devoid of tubes or otherhollows. The restrainingmeans 27 and 35 may very lightly engage thetubes 20- but it is preferable that they be spaced therefrom to assurethat the tubes will not be crushed when the re-V straining meansarebrou'ght together.V WithV the panel 24 positioned between restrainingmeans 27 and 35 las shownin FIGURE 5, and lwith the nozzle secured inthe inlet, a duid pressure is'injected into the hollows to furtherexpand the panel to the condition shown in FIGURE 6.

During Ithe second expansion the tubes 20 are again expanded into irmengagement with lthe restraining means 27 and 35 and the large hollow 21is expanded into the opening 29 in the lower means 27 and into aVsimilar opening in the restraining means 35. The panel is lfree to bedrawn in toward the-large hollow. 2l because it is not tightly clampedbetween the restraining means 27 and 35. However, warping or buckling ofthe panel is prevented by the restraining means 27 and 35 because of thevery small clearance between the restraining means and the panel. Theability of the panel to draw in is increased by applying a lubricant tothe restraining means 27 and 35. The fluid pressure within vthe panelis' released and the jaws 17 of the press are spaced apart permittingremoval of the finished panel 40. The nished panel may then be trimmedas so desired. v f

protrusions such as 36 and 37 and the cnt-out corresponding to thecut-out 29 in the restraining means 27 should be placed close to thelarge hollow 21 as manufacturing tolerances will allow.

Although this invention has been described with particulai reference tocertain embodiments, details, and techniques, various changes will beapparent to one skilled in lthe art, and the inventionis therefore notto be limited to such embodiments, details, and techniques except as setforth in the claims.

We claim:

l. The method of expanding a panel formed of super'- imposed Isheeltshaving selected portions of their adjacent surfacesY joined together todeti-nebetween said sheets a pattern of internally unjoinedV portionsdistended outwardly a iirst amount to bulge out of said panel in acorrespending desired configuration of internal hollows adapted toconiine a liuid with said hollows comprising a first hollow portion anda second hollow portion, and with said first hollow portion placed inintercommunca tion with s-aid second hollow portion, said lmethodcornprising positioning said panel between rigid restraining padsdisposed opposite said hollows, at least one of said pads having a voidencompassing said first hollow portion with Ithe remainder of said onepad having surfaces disposed ladjacent the portion of said panelopposite said second hollow portion to limit disten'tion of said secondhollow portion during subsequent expansion, and injecting fluid pressureinto said hollows to further distend by expansion said rst hollowportion into said void suiiiciently to bulge said iirst hollow portionout of said panel to a degree greater than said given iirst amount 4andto a degree greater than that of said second hollow pontion whilesimultaneously permitting said panel :to freely draw in towards saidfirst hollow portion in 'the plane of said panel during said expansion.t

2. In -a pressure Welded element having a distended internalVinter-connected fluid passageway system contained therein comprised of afirst hollow pontion and a second hollow pontion with both said portionsdistended a tirst amount and with said first hollow portion placed inintercommunication with saidV second hollow portion, a method forfurther dis-tending said rst hollow portion of said passageway systemcomprising a further distention by expansion of said passageway systemwith said panel disposed between rigid Vrestraining pads positioned op-vsaid second hollow portion to limit distention of said second hollowportion during said expansion with said expansion comprising injecting.into said system of passageways a fluid pressure to further expand saidfirst hollow portion encompas-sed by said voids sufficiently to bulgelsaid rst hollow portion out of said panel to a degree greater than thesafid given amount and to a degree greater than said second hollowportion while simultane- -ously permitting the remainder of said panelto freely draw-in in its plane between said pads towards said expandingfirst hollow portion.

3. A method of forming a relatively large passageway in a pressurewelded panel having an internal interconnected uid passageway systemadapted to confine a fluid formed therein and comprised of a firsthollow portion anda second hollow portion with both said first andsecond hollow portions distended a first amount to bulge out of saidpanel, said method comprising an expansion of said passageway systemwith the portion of said panel opposite said second hollow portionrestrained against distention lbetween a pair of opposed restrainingpads disposed adjacent said panel, said pads having surfaces disposedopposite said second hollow portion and including protrusions on saidsurfaces disposed adjacent the pressure welded web surrounding theinter-connected passageway system with said pads having a void oppositesaid first hollow portion to permit further distention thereof to adegree greater than said first amount, said expansion comprisinginjecting into said passageway system a fluid pressure to obtain saidfurther `distention of said first hollow portion outwardly of said panelinto said void with said further distention being sufficient to distendsaid first hollow portion outwardly of said panel to a degree greaterthan that of said second hollow portion while simultaneously permittingthe remainder of said panel to freely draw-in in its plane between Saidpads toward said first hollow portion during said further distentionwhereby said panel is prevented from distorting out of its plane inwhich said draw-in occurs.

4. A method of distending a panel formed of superimposed sheets havingselected portions of their adjacent surfaces joined together to definebetween said sheets a pattern of internally unjoined areas correspondingto a desired configuration of uid passageways adapted to confine a fluidwith said unjoined areas comprising a first unjoined area and a secondunjoined area with said rst unjoined area placed in intercommunicationwith said second unjoined area, said method comprising distending saidunjoined areas -a first amount, and further distending by expansion saidfirst unjoined area sufficiently to distend it a second amount outwardlyof said panel to a degree greater than said first amount while huntingthe distention of said second unjoined area outwardly of said panel torestrain the distention of said second tmjoined area `below said secondamount, `and simultaneously with said expansion permitting said panel tofreely draw-in in its plane whereby transverse distortion of said panelis restrained.

5. A method of distending a panel formed of superimposed sheets having`selected portions of their adjacent surfaces joined together to definebetween said sheets a pattern of internally unjoined areas correspondingto a desired configuration of fluid passageways adapted to confine a uidand with said areas comprising a first unjoined area and a secondunjoined area with said first unjoined area placed in intercommunicationwith said second unjoined area, said method comprising distending saidunjoined areas to the first amount desired in the portion of said fluidpassageways corresponding to said first unjoined area, and expandingsaid first unjoined area to distend it outwardly of said panel anadditional amount desired in the portion of said `fluid passagewayscorresponding to said first unjoined area While simultaneously limitingdistention of said second unjoined area out of said panel below saidadditional amount and while simultaneously permitting free movement ofsaid panel in its plane during said additional expansion whereby saidpanel is restrained against transverse distortion during said additionalexpansion.

6. The method of preventing distortion during the distention of a panelformed of superimposed sheets having selected portions of their adjacentsurfaces joined together to ldefine between said sheets a pattern ofunjoined portions corresponding to a desired system of internal fluidpassageways with said unjoined portions initially distended a firstamount to bulge out of said panel to form an intermediate configurationof said system of fluid passageways with said distended hollowscomprising a first hollow portion and a second hollow portion with saidfirst hollow portion placed in intercommunication with said secondhollow portion, said method comprising distending by expansion saidfirst hollow portion to bulge out of said panel an amount greater thansaid first amount and an amount greater than said second hollow portionand simultaneously limiting distention of said second hollow portion outof said panel `below the second said amount while simultaneouslypermitting free movement of said panel in its plane whereby said panelis restrained against transverse distortion.

7. The method of distending a panel `formed of superimposed sheetshaving selected portions of their adjacent surfaces joined together todefine between said sheets a pattern of internally unjoined portionscorresponding to a desired system of internal tubular hollows adapted toconfine a fluid within said panel with said unjoined portions beingdistended a first amount to bulge out of said panel into an intermediateconfiguration of said corresponding system of internal tubular hollowswherein said tubular hollows comprise a first tubular hollow portion anda second tubular hollow portion with said first tubular hollow portionplaced in intercommunication with said second tubular hollow portion,said method comprising positioning said panel between rigid restrainingpads spaced apart an amount slightly greater than the initial firstamount of distention of said hollows, said pads having a void oppositeto and encompassing portions of said faces opposite said first hollowportion to permit additional distention of said first hollow portion tothe degree desired in corresponding portions of said system of internaltubular hollows with the remainder of said pads having surfaces disposedadjacent the portion of said panel opposite said second hollow portionto, both, limit distention of said second hollow portion in a directionnormal to said panel and to permit movement of said panel within itsplane between said pads, injecting into said hollows a distending Huidpressure to distend said second hollow portion into firm engagement withadjacent portions of said pads and to further distend said first hollowportion into said void to a degree greater than said first amount andgreater than the distention of said second hollow portion whilesimultaneously permitting said panel to freely draw-in in its plane.

8. The method of expanding a panel formed of superimposed sheets havingselected portions of their adjacent surfaces joined together to definebetween said sheets a pattern of distended unjoined areas adapted toconfine a fluid and corresponding to a configuration of hollows desiredinternally within said panel with said unjoined areas comprising a firstunjoined area and a second unjoined area with said first unjoined areaplaced in intercommunication with said second unjoined area, said methodcomprising expanding said rst unjoined area to obtain in said firstunjoined area an additional amount of distention out of the plane ofsaid panel desired in the corresponding portion of said hollows whilesimultaneously restraining distention of said second unjoined areaoutwardly of said panel below said additional amount and whilesimultaneously permitting free movement of said panel in its planeduring said expansion whereby said 7k panelv is restrained againstdistortion transverse the plane of said panel during said expansion.

References Cited in he le of this patent UNITED STATES PATENTS 2,243,809Wendel May 27, 1941 2,498,275 Johnson V Feb. 21, 1950 2,582,358Schoellerman Jan. 15, 19,52

8 Kranenberg Aug. 18, 1953 Long Dec. 15, 1953 Grenell Sept. 28, 1954Simmons Q--- Apr. 3, 1956 Watter Aug. 19, 1958 Adams Nov. 11, 1958Rieppei Apr. 21, 1959 Simms Aug. 11, 1959

